Aphids of the wheat and action of parasitoids in the district of Augusto Pestana, northwest of the Rio Grande do Sul state, Brazi

Abstract

The understanding of ecological relationships is fundamental to the implementation of strategies to aphids pest management in agroecosystems. The objective of this work was to evaluate the occurrence of aphids associates to the culture of the wheat and the level of natural parasitism in crops with different management plant. The study it was carried through in the district of Augusto Pestana, Rio Grande do Sul, Brazil, in five experimental units (crops) of the 3500m2. The populations of aphids had been monitored by weekly sampling from the period of training of tiller until the period of physiological maturation of the culture. Four species of aphids had been diagnosised: Sitobion avenae (87%), Rhopalosiphum padi (8.3%), Schizaphis graminum (3.9%) and Metopolophium dirhodum (0.8%). The number of aphids found incrops did not reach 10 aphids/tiller during the study, possibly in result of the use of insecticides in these places. The natural parasitation were observed during study and the population growth followed the aphids population in crop. Records the occurrence of Aphidius uzbekistanicus and Aphidius sp.